Total-radiation pyrometer



July 9, 1957 E. M. woRMsER TOTAL-RADIATION PYROMETER 2 Sheelcs-Sheet l Original Filed Jung 30. 1951 lllllIllllmllillllllllll Suventor (Ittornegs July 9, 1957 E. M. woRMsER 2,798,961

TOTAL-RADIATION PYROMETER Original Filed June 50. 1951 2 Sheets-Sheet 2 Gttornegs TOTAL-RADIATIN PYRONETER Eric M. Wormser, New York, N. Y., assigner to Servo Corporation of America, New Hyde Parli, N. Y., a corporation of New York Original application .lune 30, 1951, Serial No. 234,483, now Patent No. 2,761,072, dated August 28, v1956. Divided and this application July 18, 1956, Serial No. 608,644

9 Claims. (Cl. Z50-$3.31)

My invention relates to radiation pyrometers, that is, to instruments for evaluating the radiation intensity of a given source. y

This application is a division of my prior application Serial No. 234,483, iiled June 30, 1951, for Total Radiation Pyrometer; now U. S. Patent No. 2,761,072.

lt is an object of the invention to provide an improved device of the character indicated.

lt is another object `to provide improved means for measuring heat radiation.

It is also an object to provide heat-radiation measuring means employing improved visual-sighting optics.

A further object is to provide improved means for Calibrating a radiation pyrometer.

It is a general object to meet the above objects with a compact and easily handled assembly that is simple to use and relatively unaffected by constant abuse.

Other objects and various further features of the invention will be pointed out or Will occur to those skilled in the art from a reading of the following specication in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

Fig. 1 is a vertical sectional view along the axis of a portable radiation pyrometer incorporating features of the invention;

Fig. 2 is a left-end view of the pyrometer of Fig. 1;

Fig. 3 is au enlarged sectional View of a part of the pyrometer of Fig. 1, as taken in the plane 3-3 of Fig. l;

Fig. 4 is a simplified block diagram, schematically illustrating electric components which may be utilized in conjunction with optical components of Fig. 1;

Fig. 5 is an optical diagram, schematically illustrating an alternative optical arrangement;

Fig. 6 is a front three-quarter perspective view of a portable pyrometer generally similar to that of Fig. 1 but incorporating slight modifications; and

Fig. 7 is an optical diagram schematically illustrating a still further arrangement.

Briefly stated, my invention contemplates novel optied combinations and arrangements for use in'radiationresponsive measurements in and near the visible spectrum, as for example in the so-called far-infrared region, out of say microns. Such combinations may utilize visual-sighting optics at least partially in common with, or on a common axis with, the optics for focussing a distant radiation source upon the radiation-responsive means, whereby parallax problems are avoided. Means may be incorporated in, or employed in conjunction,

arent Patented July 9, 1957 radiation-responsive means may be checked and calibrated as frequently as desired.

Referring to Figs. 1 to 4 of the drawings, my invention is shown in application to a portable radiation pyrometer in which the optics may be substantially contained in a cylindrical body or housing 10. It is a feature of the embodiment of Figs. 1 to 3 that visual-sighting optics including an eyepiece 11 are lined on an axis common with the axis of the collecting optics for the radiation-responsive means. The radiation-responsive means may comprise a heat-sensitive cell 12 contained in a suitable housing 13 and mounted upon a standard 14 extending radially into the housing 10. In the form shown, microphonics in the heat-responsive means 12 and its associated mplifying means are materially reduced by assembling the housing 13, the standard 14, and preamplifier means 1S together as a unit; this subassembly may be mounted and adjusted as a unit on and within the body or housing 141. A longitudinal slot 16 at the front end of the housing 10 may permit slidable insertion of this heat-responsive assembly in clearance with the standard 14.

The collecting optics may comprise a parabolic mirror 17 mounted at the back end of the body 1t). In the form shown, the mirror 17 is carried by a sleeve 18 slidable longitudinally in a counterbore 19 in the housing 1t), for focusing purposes. The focusing means shown includes a knurled ring 211 with a shank 21 threaded into a back plate 22 forming part of the pyrometer housing 1t). The mirror assembly 17-18 includes a back plate 23 keyed, as at 24, against rotation with respect to the housing 1li. A shoulder engagement at 25 between the threaded shank 21 and the mirror backing plate 23 provides a means whereby longitudinal adjustment eifected by the knurled ring 211 may be directly translated to the mirror 17 for focusing purposes. The two rays 26 in Fig. l illustrate radiation from a distant source (not shown) focused upon the heat-responsive means 12.

ln the form of Figs. 1 and 2, I employ a small fixed mirror 27 to intercept a part of the radiation which would otherwise be focused upon the heat-responsive means 12 and to reflect this part of the radiation into the visualsighting optics. Thus, whenever the mirror 17 is adjusted, as for purposes of focusing on the heat-responsive means 12, the radiation employed for visual sighting will also be focused at an imaginary location 28, spaced conjugate to the plate of the heat-responsive means 12 with respect to the mirror surface 27. Rays, such as the rays 29, inter-' cepted by mirror 27, will thus cross over at the point 28, and the lenses 30 of the visual-sighting optics may be set for focus on this point 2d. A cross-hair reticule 40 at a ray crossover in the sighting optics 11 may assist in alignment of the device on a given source to be observed. It will be appreciated that, once adjusted, both the visualsighting optics and the collecting optics will always be focused at the same collecting distance. Whenever the knurled ring 2d is rotated to focus for another collecting distance, both the sighting optics and the cell will maintain focusing alignment.

The heat-responsive means 12 is preferably rugged and may be one of several types; I prefer to use so-called thermistor means in the cell 12, and in Fig. 4 l illustrate the employment of two thermistor strips 12-31. The strip 12 responds to radiation collected and focused by the optical head 32, which may be that shown and described in Figs. 1 and 2; but the strip 31 is not exposed to radiation and acts as a compensator for ambient conditions. D.C. drift and other diieulties may be avoided by deliberately effectively chopping the radiation focussed upon the radiation-responsive strip 12. This may be accomplished electrically by appropriate modulations in the circuit including the strip 12, or, as in the form shown.

a mechanical chopping disc 33 may be mounted for rotation so as to interrupt the impingement ofradiation uponA Y shaft upon which the chopping disc 33 and its drive pulley 37 are mounted. In Fig. 4, the dotted square wave 32' schematically represents interrupted radiation passed by the optical head 32 to the exposed thermistor strip 12.

In the form shown, the radiation-responsive thermistor 12 and the compensating thermistor 31 are mounted in conjugate arms of a bridge circuit. Power supply 42 may energize the bridge, and the bridge output may be fed through signal-attenuator means 43 to preamplifier 15; the attenuating means 43 may be included in the preamplifier package 15. The preamplilied signal may be fed by a cable (not shown) to a narrow-band amplifier 44 in order to eliminate undesired modulation products,

and rectifying means 45 and power-amplifier and attenuator means 46 may shape the envelope of heat-responsive signal appropriately for visual display on a meter 47 and for recording on a conventional recorder 48.

In Fig. 5, I illustrate an alternative optical arrangement providing a more exact basis for quantitative heat measurement, with relatively little additional complexity. The arrangement of Fig. may also be characterized by coincidence of the axis of visual sighting with the axis of the collecting optics for heat-responsive means 50. However, in the arrangement of Fig. 5, the thermistor or other heatresponsive element of the means 50 is alternatively exposed to radiation collected by the optics and to radiation from a regulated reference source 51, which may be a so-called black body of carefully regulated temperature and including optics 52 focussed upon the heat-responsive means 50. The collecting optics shown in Fig. 5 is of the so-called Cassegrain system employing a large concave primary mirror 53 and a small convex secondary mirror 54. Rays collected by the mirrors 53--54 may be passed through an opening 55 in the center of the primary mirror 53 and may be focused at a cross-over point 56, back of the mirror 53; I have shown a reticule 57 at the cross-over point, for purposes of pin-point sighting alignment of the device (by means of a viewer 58) upon a particular distant source of radiation tobe observed. In order that the heat-responsive means 50 may be exposed alternately to the reference radiation from the source 51 and to the distant radiation collected by the optics 53-54, I employ a chopping disc 59 having a plane mirror surface. Whenever the chopping disc 59'is in position to blanket radiation from the reference source 51, the mirror surface 59 of thechopping disc may be reflecting the distant-collected radiation upon the heat-responsive means 50; whenever the chopping disc 59 is not reiiecting such distant-collected energy, it is eiectively open so as to expose the heat-responsive means 50 to the reference source 51. It will be appreciated that by employing the heat-responsive means 50 in conjunction with signal-processing means like that of Fig. 4, one may quantitatively record or observe signals representing the difference between the reference radiation (at 51) and the distant radiation (as focusedY by the collecting optics). y

In Fig. 6, I show a simple readily portable pyrometer instrument having many of the structural features already discussed in connection with Figs. l to 3. In the arrangement of Fig. 6, however, the visual-sighting optics does not utilize the main collecting mirror (not shown) Vfor the heat-responsive means 60. Such mirror will be understood to be paraboloidal, as in the case of the mirror 17 of Fig. 1 and contained within the cylindrical housing 61.V The heat-responsive means may again be mounted upon a standard 62 carried by the preampliiier housing 63 and received through a slot 64 at the forward end of the cylindrical housing 61. Chopping means 65 for the incident-radiation may be drivenl by an externally mounted motor 66. Even though the visual-sighting optics may not use any part of the collecting optics, parallax diniculties may be avoided by employment of an off-axis sight including a small periscope aligned with the axis of the collecting optics. In the form shown, the visual-sighting means employs an eyepiece 67 on a telescope 68, clamped rigidly to the outside of the housing 61; two 45-mirror elements 69-70 connected by a tube 71 provide the necessary offset for the periscope, the reflecting axis of the entrance mirror 70 being on the axis of the collecting optics.

In Fig. 7, I show a more refined pyrometer incorporating certain features over the arrangement shown in Fig. v5. As in the case of Fig. 5, the collecting optics may be a Cassegrain system, with a concave primary minor and a convex secondary mirror 76, the focal length of the system being relatively long so that the focal point will lie substantially to the rear of the primary mirror. For precise sighting, a reticule 77 may be placed at the focal point, and telescopic viewing means 78 may be placed beyond the focal point. As also in the case of Fig. 5, a rotating-mirror chopping disc 79 may permit heat-responsive means 80 to look alternately at rays projected by the collecting optics 75-76 and at rays projected by the lens 81" of ra reference source 82. As thus described, the system of Fig. 7 is the exact duplicate of that of Fig. 5, and recorded or otherwise observed signalsy emanating from the heat-responsive means 80 will present effectively continuous comparison between the distant radiation and the reference radiation.

In spite of the ascertainable relation (utilizing the parts thus far described in Fig. 7) between the distant radiation and the reference radiation, instrument responsivity remains as an unknown factor. This isparticularly true in particular applications in which a restricted portion of the spectrum is being examined, for the heatresponsive means 80 is likely to have various responsivities for various wavelengths. In order to make the responsivity readily ascertainable when desired, even while making a measurement, I may provide what I call a calibrating source 83 which may, like the black body or reference source 82, be a constant radiator of carefully regulated temperature, withY optical means 84 for focusing upon the heat-responsive means 80 when desired. In the form shown, a pivotally mounted plane mirror 85 is so arranged as to be normally out of the path of rays projected by the collecting optics 75-76. However, when desired, the mirror 85 may be manually depressed against a stop 86 so as to hold a retiecting position blanking off rays from the collecting optics and casting rays from the calibrating source 83 directly upon the heat-responsive means 80 in a cycle of alternation with rays projected from the reference source 82.

Inr use, thecalibration source 83 is regulated at a temperature of the order of magnitude of the temperature to be observed through the collecting optics, that is, of the order of magnitude yof the temperature of the distant source, and the reference source 82 is set for some substantially different temperature. For example, if the distant source to be observed has a temperature of about.

to 200 C, then the temperature of the calibrating source 83 might be conveniently regulated at 150 C., while the reference source isregulated at about 80 C. Such regulation may be accomplished within 0.1 C. by meansnot shown or described herein.

In use, with the manually operable mirror 85 in the raised position, the measurable voltage in the heat-responsive means 80 will reect the difference in radiation between the distant source and the reference source 82. This relationship will be characterized by an instrument responsivity which appears as a constant. When the mirror 85 is depressed, the voltage in the output of heatresponsive means 80 will reflect the difference in radiation between the reference source 82 and the calibrating source 83, and an instrument responsivity will appear as a constant in this relationship. The instrument will presumably have been calibrated initially for a given responsivity, characterizing alternating exposure between the reference source 82 and the Calibrating source 83; thus, in field use, if a voltage other than the original calibrated voltage is observed when the mirror 85 is depressed, then the observed percentage voltage change under these conditions will be a measure of the change in responsivity of the instrument, and an appropriate correcting factor will be available for application to the voltage reading obtained when the mirror 85 is retracted out of the way of rays from the collecting ioptics. More highly refined measurements may be made in this manner.

It will be seen that I have disclosed relatively simple pyrometer constructions featuring ruggedness for the accuracy obtainable. The optical-sighting arrangements and the relative compactness permit easy handling and precise focussing and alignment with sources to be observed, whether at close or distant range. With little additional complexity, means may be provided for more exact quantitative determinations, and instrument responsivity may be checked at any time, thus providing an appropriate correction factor whenever an instrument reading is taken.

While I have described my invention in detail for the preferred forms shown, it will be understood that modifications may be made within the scope of the invention as defined in the appended claims.

I claim:

1. In a radiation pynometer, radiation-responsive means, collecting optics including a mirror having a curved surface of revolution about an axis including said radiation-responsive means, whereby a distant radiation source may be focused upon said radiation-responsive means, mirror means interposed between said radiationresponsive means and said curved mirror and intercepting a relatively small bundle of the total rays focused by said curved surface upon said radiation-responsive means, and visual-sighting means aligned with the reflecting axis Iof said mirror means 2. A pyrometer according to claim 1, in which said radiation-responsive means includes chopping means disposed between said mirror means and a radiation-responsive element of said radiation-responsive means, whereby the chopping operation may be used substantially only in the control of the response of said radiation-responsive means and whereby visual sighting may be unaffected by chopping.

3. In a radiation pyrometer, collecting optics for converging to a focal point radiation from a distant source, radiation-responsive means at said focal point, a plane mirror on the axis of said optics and disposed in the converging rays of said o-ptics at a location spaced from said radiation-responsive means, and viewing means for rays reected by said plane mirror.

4. A radiation pyrometer, comprising a housing having an elongated bore open at one end thereof and having an access opening in the wall thereof near said open end, collecting optics including a relatively large mirror closing the other end of said bore and facing out the open end on an optical axis generally aligned with that of said bore, said mirror having a central opening therein, a radiation-responsive unit comprising `a base and a cell and an elongated thin support mounting said cell remote from said base, said base being longitudinally adjustably secured to said housing with said support passing through said opening and with said cell facing said mirror on said optical axis, whereby said cell may be located at the focal point of said collecting optics, radiation-chopping means between said mirror and said cell for converting radiation focused on said cell into an A. C. signal, and visual-sighting optics including a relatively small mirror on said optical axis between said chopping means and said relatively large mirror.

5. A pyrometer according to claim 4, in which said base houses a preamplifier for the output of said cell.

6. A radiation pyrometer, comprising a tubular housing having a closed end and a bore open at the other end, said housing having angularly spaced side-access openings near said open end, a collecting mirror mounted within said closed end on an optical axis generally aligned with that of said bore, said collecting mirror having a central opening therein, a radiation-responsive aS- sembly comprising a base and a cell and an elongated thin standard xedly mounting said cell remote from said base, means securing said base externally of said housing with said standard passing through one of said openings and with said cell facing said mirror at the focus of said mirror, a radiation-chopping assembly comprising a base and a chopper and an elongated thin standard mounting said chopper remote from said base, means securing said second-mentioned base externally of said housing with said second standard passing through another of said openings and with said chopper between said cell and said mirror, a relatively small plane mirror between said chopper and said collecting mirror and facing said mirror opening on the axis thereof, and a visualsighting optical assembly including a sighting barrel aligned with said plane mirror through the opening in said collecting mirror.

7. A pyrometer according to claim 6, in which the base for said chopping assembly includes drive means for said chopper.

8. A pyrometer according to claim 7, in which a continuous belt connects said drive means to said chopper and extends through said other opening.

9. A pyrometer according to claim 6, in which said collecting mirror is longitudinally adjustably displaceable in said housing and in which said visual-sighting optical assembly includes adjustable focusing means, and means connecting the adjustable parts of said mirror and visual-sighting assembly for coupled focusing of Said pyrometer.

References Cited in the file of this patent UNITED STATES PATENTS 

